Single-row metric TS, single-row imperial TS, and double-row TDO/TDI are the three structures an engineer must choose between before any tapered roller bearing [S4] hits the BOM line, with each design tied to a specific load vector and speed window.
Selection is driven by six gates in fixed order: load vector and magnitude, basic dynamic load rating C, permissible speed n, ISO tolerance class (P0/P6/P5/P4), mounting arrangement (DB, DF, O-arrangement with spacer), and lubrication envelope [S1][S3][S4].
Gate 1 — Load Vector: Why Tapered Exists At All
A tapered roller bearing carries combined radial + axial load in one direction simultaneously — the line contact between the conical rollers and the raceways projects the radial reaction onto the cup shoulder, so a single row handles both load components when paired in a DB back-to-back or DF face-to-face stack [S4].
Plain deep-groove ball bearings only handle light axial loads as a side effect; needle rollers carry pure radial load. When the application sheet shows an axial load above ~25% of the radial load, or thrust must be located positively, a tapered roller bearing becomes the default rather than a fallback [S1][S4].
Gate 2 — Type Codes: TS / TSF / TSL / TDO / TDI / TNA
The Type TS metric single-row is the workhorse: cone + cup + rollers in a separable package, widely used in automotive gearboxes and industrial gearboxes at bore sizes 20–320 mm [S4]. Type TSF adds a flange on the cup for axial location in sheet-metal housings; Type TSL adds the flange to the cone for the opposite orientation [S4].
Double-row Type TDO (two single-row cones, one double cup) and Type TDI (two single-row cups, one double cone) double the load capacity and provide a stiffer system, at the cost of a longer overall envelope and a more demanding bore tolerance [S4]. Type TNA / TNASW / TNASWE add a flanged double-cup variant for press-fit housings [S4].
Gate 3 — Capacity and Speed: Reading C and n×dm
Basic dynamic load rating C is the radial load (in kN) that 90% of a population can survive for 1 million revolutions under ISO 281 test conditions; required life L10h = (C/P)^p × 10^6 / (60·n), with p = 10/3 for roller bearings [S1].
Permissible speed n scales inversely with the mean diameter dm — most single-row TS catalog values cap continuous oil-air lubrication at roughly 2,500–3,000 rpm in mid-size 320xx series, with grease lubrication limited to ~60% of oil-air rating [S1]. Exceeding n·dm ~ 0.6 × 10^6 mm·rpm is the classic early-failure trigger for caged steel rollers.
Gate 4 — Tolerance Class: P0 / P6 / P5 / P4 in Context
ISO 492 classes P0 (ABEC 1), P6 (ABEC 3), P5 (ABEC 5), P4 (ABEC 7) govern bore, OD, and running accuracy; the bulk of automotive and industrial gearbox usage sits at P0 / P6, with P5 reserved for machine-tool spindles and P4 for high-precision grinding spindles [S1].
Mass-produced automotive tapered roller bearings at P6 / P5 grade with 22×47×15.25 mm and 32×65×25.9 mm footprints are commodity items supplied in large volume from Chinese manufacturing clusters, while P4-class units for spindle duty command a multiple on lead time and price [S3].
Gate 5 — Material, Cage, and Lubrication Envelope
Through-hardening chromium steel (AISI 52100 / DIN 100Cr6) is the default for most single-row TS parts; case-carburised variants (e.g. 20CrNi4) are standard for railway axle-box and heavy industrial gear drives where subsurface shear stress dominates [S1].
Cage options are pressed-steel (cost-driven, -30 °C to +120 °C), brass machined (heavy-duty, higher speed), and polyamide 66 (quiet running, -40 °C to +150 °C, light load only). Selecting brass over PA66 is mandatory when continuous oil temperatures exceed 150 °C or when peak n·dm exceeds the polyamide limit [S1].
Gate 6 — Mounting, Sealing, and Trade vs General
For metric TS parts under HS code 8482.20 (tapered roller bearings including cone and cup assemblies), MFN import duty into the EU sits in the 1.7%–2.7% band under the current EU CCT, with origin China [S2]. Buyers should confirm whether the supplier quotes the complete assembly (cone + cup) or the separate cone/cup components, as the duty treatment and lead time differ.
Mounting arrangement is the last gate: O-arrangement (two cones back-to-back on a common shaft with separate cups) is the most common industrial-gearbox layout; X-arrangement (cones face-to-face) is reserved for short shafts. Setting preload by grinding the cup spacer or shimming the cone spacer determines axial rigidity — and is the single biggest source of premature tapered-roller failure when done by feel rather than by torque-gauged method [S1][S4].
Brand Provenance and the Default-Risk Lens
Timken (USA, founded 1895 by Henry Timken on the tapered-roller concept) and INA (Germany, founded 1946, part of the Schaeffler Group since the merger) are the two engineering brand anchors for the format; both publish full TS/TDO/TDI catalogs and back their catalog C values with documented ISO 281 test data [S6][S7]. NSK Europe also lists thin-section single-row steel variants in its industrial line-up for gear and general machinery duty [S1].
When the spec sheet says "tapered roller bearing" without a brand, the dominant volume comes from Chinese manufacturing clusters around Linqing/Guanxian; factory-direct quotations at P6 grade are common, but buyers should request the heat-treatment certification (J9 / JB/T 53810) and a runout report before accepting the first shipment [S3][S5]. For a side-by-side frame on how a roller bearing family decision changes the spec, the six-gate article on SourceBySpec covers the same gate order for cylindrical, needle, and spherical formats in parallel.
Trackable signals for the next purchasing cycle: 320xx-series P6 stock availability at 22×47×15.25 and 32×65×25.9 footprints in the 6,000–8,000-piece monthly run rate; brass-cage vs pressed-steel price spread on TDO double-row; and the EU 8482.20 duty band on China-origin imports referenced under the current EU CCT [S2][S3].
For component-level specifications, see road roller.
For related coverage, see Stainless Steel vs Copper: Selection Criteria, Conductivity Gap, and 2026 Spec Frame.